This sounds very similar to what my 18 year old daughter is going through. She has Behcet’s (diagnosed in 2017). She recently had a sudden syncope episode on 1/24/24 and since has had weight gain and severe weakness. Cortisol and ACTH are critically low so they diagnosed her with central adrenal insufficiency and started her on steroids. The steroids haven’t helped and have just made the weight gain worse. She still has all the fatigue and weakness, plus the negative side effects of the steroids. They can’t find a cause for the central adrenal insufficiency. She’s had 2 MRI’s in the past 3 months and both are normal. She feels terrible and we aren’t getting any answers. She has several specialists at UNC medical center including an endocrinologist. We did just send all of her records for an evaluation at Mayo Clinic in Minnesota and I’m waiting to hear back.